1. Field of the Invention
The present invention relates to a cubic boron nitride (cBN) sintered body, particularly to a cBN sintered body for use in cutting tools that are improved in wear resistance and chipping resistance.
2. Description of the Background Art
Because cBN is the substance next to diamond in hardness, cBN-base sintered bodies have been used in cutting tools, wear-resistant parts, impact-resistance parts, etc. This type of sintered body has difficulty in achieving both high hardness and high strength. Published Japanese patent applications Tokukosho 62-25630, Tokukosho 62-25631, and Tokukaihei 5-186272 have disclosed techniques aiming at the achievement of the compatibility of hardness and strength. The disclosed techniques, however, have not necessarily been sufficient in the compatibility of hardness and strength. For instance, single point tools comprising the foregoing sintered body, when used in high-speed cutting, allow the flank wear and crater wear to sharpen the cutting edge, resulting in easy chipping of the cutting edge. Even with ordinary cutting speeds, the tools tend to suffer chipping of the cutting edge from an impact when used in applications where strong impacts are applied as in interrupted cutting. Those drawbacks have lead to unstable tool life.